Method in the production of compression moulded objects



Jan. 5, 1965 J. R. FRANKSSON METHOD IN THE PRODUCTION OF COMPRESSION MOULDEID OBJECTS Filed Oct. 16, 1961 DRIED PARTICLES RESIN BLENDING MOISTURE CONTENT OF 345% MAT FORMATION PRE- PRESSING FLAT PRESSING SWELLING IN WATER OR STEAM AFTER SWELLING v DRYING TRIMMING ADDITIVES INVENTOR JAN ROLF FRANKSSON ATTORNEY United States Patent r 3,164,648 METHOD IN THE PRODUCTION OF COMPRES- SION MOULDED OBJECTS Jan Rolf Franksson, Nacka, Sweden, assignor to Aktiebolaget Casco, Stockholm, Sweden, a Swedish jointstock company Filed Oct. 16, 1961, Ser. No. 145,500 Claims priority, application Sweden, 'Oct. 24, 1960, 10,189/60 5 Claims. (Cl. 264-109) gasse and so on. These objects are produced under heat and pressure with the aid of a resinous bonding agent. The method is described below in connection with the production of chipboards, but it is implied that it may be used in applicable parts also to other materials.

The manufacture of chipboards has lately got an ever increasing extent. Generally chips are now made from high quality cut wood material which is dried to a moisture content considered suitable in glueing (3 to 15%). Moisture content in the present sense is understood to be the ratio between the amount of moisture and the quantity of the dried material. Usually the glue is spread directly on to the dried chips. The glue types now used commercially consist of urea resin glue, phenolic resin glue, and melamine-urea resin glue. An important property of the finished board and of compression moulded products is the dimensional stability of the product at varying moisture contents. In order to obtain the desired dimensional stability, one has been heretofore compelled to supply a moisture repellent agent to the chips, said It has been observed that a urea resin parallel with the plane of the'board is normally subjected with boards glued with melamine-urea resin. When using conventional phenolicresin glues the thickness -increase for such boards amounts to not less than about 15 to 30% after storing in water for 24 hours. In chipboards which have been moulded with the chips perpendicularly to the plane of the board the change of the dimensions at varying moisture contents will substantially constitute an equally great percentual change of the length and width of the board.

The cost of materials and the properties of the finishedchipboards depend to a, great extent upon the bulk density which, as regards commercial products, varies Within rather wide limits (urearesin boards 0.50-0.70 tons/m. phenolic resin glued board 0.65 to'0.8O tons/ m.

It has now been discovered in the present invention that chipboards once swollen and redried can be remoistened to have a substantial volume increase remaining and stabilized, e.g., *that'the' boards treated by the method of the invention will have a remarkably high degree of dimensional stability after renewed moistening. This characteristic property of chipboards is, according to the present invention, utilized for the production of a dimensionally stable product with low bulk density. It is in fact possible to obtain about 20% lower bulk density and swelling of 3 to 5% after storing for 24 hours in water, which must be considered as an extremely good value, especially with respect to the fact that no moisture repellent agent is added. T he strength of board material thus treated is generally unchanged after dryingand sube C. :the press time is 10 minutes.

,upon the climate conditions.

stantially quite comparable with that of commercial untreated boards.

The characteristic feature of the method according to the present invention is that the moulded objects are retreated to be given a moisture content exceeding 20%, e.g. 20 to and are thereafter dried and trimmed. The desired moisture content can be obtained by soaking the objects in water or treating them with steam. Simultaneouslywith this rehumidifying treatment a' fireproof agent may be added and also antimicrobialchemicals may be supplied for protection against rot, termite attacks and so on. The drying is carried out to a controlled moisture content of 6 to 20%.

In the production of chip board the the chips are first dried in the usualmanner whereafter the glue binder is spread thereover. As a rule, it is not desirable to add a moisture repellent agent because this only delays the swelling at the subsequent treatment and works harm to carrying out the present method. After the glued, untrimmed boards have been hardened, the edges are sawed, whereupon they are soaked in water and, for example, are piled horizontally in packs suring soak. The water soaking shall be extended only over a time sufiicient to supply as much water to the boards as the wood or the material contained in the boards needs to reach its fiber saturation point. Of course, more water may be added without sacrificing the quality of the finished product. Depending upon the species of chips .used, the boards can be soaked until the moisture content reaches 100% .or even However, this results in prolonged drying time and subsequent decrease of economy since in any case, the boards must be dried to attain the desired final moisture content. For out-of-door use the boards may be dried to about 18%, for carpenters purposes to about 13% and for furniture manufacture to about 8% m0isture content. These values are, of course, dependent After drying the boards are trimmed in the usual manner.

The advantages obtained accordingto the present meth-" od are as follows: t

(l) Boards with high dimensional stability can be produced. 1 I

(2) Boards with low bulk density and maintained strength properties are obtained. This means a considerable saving of materialfi Phenolic resin glued, weatherproof boards can therefore be produced at about the same cost as urea resin glued standard boards in spite of the extra cost for swelling and drying.

(3) Moisture repellent agents need not be added.

(4) The .boards can be impregnated atv a low cost against termite attacks, fire, rot and so on.

The method according to the invention is illustrated more particularly with reference to the following examples. y e

- t Example 1 The resin content is 7% calculated upon dried chips in the surface layer and to 6% in the middle layer. No moisture repellent agent is added. The bulk'density of the board amounts to 0.685 g./cm. and its thickness is 10 mm. At a compression moulding temperatureof 150 1 The closing time is 30 seconds. j

After compression, the board is sawed to the size 225 x 225 mm, and the sawed boards are stacked thereafter horizontally in piles and soaked in a water bath at 20 C. for 2 hours. The boards are now swollen about 18% in thickness at 50% water absorptionfand are dried in 3 a drying closet to about 13% moisture content at 60 C, During the first part of the drying, the boards continue to swell to a thickness increase of about 25% due to the hot steaming to which they are subjected at the p 4 Example 3 In connection with the swelling of the thickness effected in the Examples 1 and 2, fireproof agents were supplied to the boards. The water bath contained 20% In the same way as in Example 1 tests were made with urea resin glued chipboard, The moisture content of the surface chips amounted to about 7% before the glueing .and that of the intermediate chips to about 5%. The

A begumngt g fi g i fi i i 1t 5 of fireproof agent. The chipboards were soaked long can 6 es a i e l S enough in the water bath mixture in order to absorb a 3?? i; a T651 SW6 mg t ass 0 a on quantity of fireproof agent sufficient to obtain resistance f g 2 g th tri d th 31 to flammability. The water swelling properties and the i b 2 S en 2 m a strength of the boards were not deteriorated by this firei i h 6 2 .15 i i 10 proof impregnation. The bulk density which decreased 0 t c Hess a Sur p 1s 0 i without fireproof agents, was in this case almost un- Whlch 18 fully comparaijle dlmenslona'ny i the requlre changed due to the fact that the boards absorbed about ment for standard chipboard. The testing of treated 10% of fireproof agent (see Table 1) boards indicates excellent quality. The subsequent swelling in water after 24 hours is scarcely 5% and after 96 Example 4 hoursscarcely The transversal tenslle strength 18 Chipboards were produced in the conventional manner scarcely 5 kg./cm. and the bendlng strength about 400 from pine Chips according to the method Stated in kg./crn. V Untreated boards swell after 24 hours to 22% ample 1 fi t paragraph, and wars kept horizontally in and aftel: 96 hours to about transversfll a water bath which contained a 3% aqueous solution of strength 15 about 5 kg/cm? and bendmg stljenglh 0 a wood impregnation agent consisting of copper salts and about l i Y melhod 0f the pentachloro'phenol. After 24 hours storing in water, an tion, a lighter chipboard 1s obtained having a bulk density average moisture content f 93% was Obtained: which Whlch dficl'eased 3 lfl f to 1 after further 120 hours storing in water had risen to 11101801115 Content- The orlgilnal q Strength 142%. The boards were then placed in a drying closet retam'efi, the Water Swenmg Proper/es are unmoved; and, 25 for three hours and were dried to 10% moisture content at boiling tests, the board proves to be acceptablyweathat C, ft which they e tested in the Same so that can be used R Wlthout ner as the products according to the foregoing examples. risk of undue warping based on moisture changes. Th6 There was no difierence between these boards and the results Wlnbe 56611111 boards produced according to the previous tests as re- Order t0 ShOW that ShI111k11'1g d0eS not P at lower gard-s swelling. Strength and dimensional stability of the moisture contents, boards were dried to moisture contents fini h d b d were quite comparable i the results between 0 and 3%. These b a s d not r k f obtained according to Example 1. On the other hand, ther, but the thickness swelling of about 20% Was mainthe drying time was extended due to the greater quantity tained. of water which had to be removed by drying.

TABLE 1 Swelling in water, percent Water absorption, Strength lrgJcm.

percent Bulk 7 Ex. density .Transversal Bending 2 hrs. 24 hrs. 96 hrs. Max. 2 hrs. 24 hrs. tensile strength strength Phenolic resin glued chipboard treated 3. 5T 4. 6 5. 6 ca. 8-.." '39 49 5. 3 400 0.595 according to the invention.

1 Phenolic resin glued chipboard with- 17. 5 22 28 ca. 30--.. 50 70 5.4 n 450 0.685

out moisture repellent agents. I Phenolic resin glued chipboard with 5. 5 16 24 ca. 30...- 20 5.0 450 0. (S90 moisture repellent agents. Urea resin glued chipboard treated ac- 4. 5 8 10 30 40 2. 5 200 0. 550

cording to the invention. 2 Urea resin glued chipboard 'wlthout 17.5 I 22 28 77 4.0 290 0.650

moisture repellent agents. Urea resin glued chipboard standard 5. 5 n 10 24 19 43 4.0 230 0.650

with moisture repellent agents. 3 Phenolicresingluedchipboard accord- 3.7 4.8 5.7: ca. 8 41 50 5.2 400 0.660

. ing to the invention with fireprooi- I impregnation.

ExampIe Z What I claim is:

.chips in the dry state being surface treated with a water repellent agent was used. The bulk density of the boards was 0.65 and their thickness was 19 mm. The compression moulding temperature was 140 C. and the press time was 10minutes.- The closing time was 30 seconds.

In'this case, the properties of the boards were also characterized by low swelling in water. On the other hand, they were not weather-proof.- The bulk density of the boards diminished only from 0.65 to 0.55 by the 20% increase of thickness; The boardscompressed to a thickness of h 19 mm. had, after swelling in water and drying, a thickness of almost 23 mm. After trimming to a thick ness of 20 mm. the surfaces were acceptable within standard requirements. The results will be: seen in Table resistant thermosetting synthetic resin binder selected from the class consisting of phenol formaldehyde resin, ureaformaldehyde resin, and melamine formaldehyde "resin and thereafter formed as a sheet by-molding under heat and pressure; that improvement for stabilizing the thick ness dimension of the molded particle board after mold- 1 5 i reduced below 20% and down to 6% by Weight of said dry sheet and trimming the dried sheet, to reduce the thickness to the predetermined value whereby a dimensionally stabilized board is produced,

2. A method as claimed in claim 1 wherein the molded aldehyde and the board is cut into units, the units put into stacks and the stacks are immersed in a water bath at room temperature for several hours to achieve an increase in thickness of about 20% 4. A method as claimed in claim 1 wherein the molded particle board is made of fir chips and the resin is melamine formaldehyde.

, i 6 1 5. 7 A method as claimed in claim 1 wherein the molded particle board is treated with steam in order to bring about a pick-up of moisture greater than 20% References Cited by the Examiner UNITED STATES PATENTS' 2,638,421 5/53 Serres 1847.5 XR 2,743,758 5/58 Uschmann 18-475 XR 2,876,153 3/59 Dorland et al. 18-47.5 XR 2,994,620 8/61 Franck et al.

OTHER REFERENCES Conditioning Particle Boards (R. Fischer), FAO/ EOE/BOARD CONS, paper 5.37.

Fiberboard and Particle Board, published by Food and Agriculture Organization of the UN. (printed 1958),

pages 9, 51, 52, 63, 67, 68, 73 and 74. ALEXANDER H. BRODMERKEL, Primary Examiner.

2o RICHARD D. NEVIUS, Examiner. 

1. IN THE MANUFACTURE OF COMPRESSED CELLULOSIC PARTICLE BOARD CONSISTING OF NON-DEFIBRATED WOOD CHIPS HAVING A MOISTURE CONTENT OF FROM 3 TO 15%, SAID CHIPS HAVING DIFFERENT MOISTURE SWELLING CHARACTERISTICS ALONG THE DIRECTION OF THE CELLULOSIC FIBERS THAN TRANSVERSE THERETO; SAID WOOD CHIPS IN THE DRY STATE BEING SURFACE TREATED WITH A WATER RESISTANT THERMOSETTING SYNTHETIC RESIN BINDER SELECTED FROM THE CLASS CONSISTING OF PHENOL FORMALDEHYDE RESIN, UREAFORMALDEHYDE RESIN, AND MELAMINE FORMALDEHYDE RESIN AND THEREAFTER FORMED AS A SHEET BY MOLDING UNDER HEAT AND PRESSURE; THAT IMPROVEMENT FOR STABILIZING THE THICKNESS DIMENSION OF THE MOLDED PARTICLE BOARD AFTER MOLDING AND PRIOR TO STORING AND USING CONSISTING OF UNIFORMLY IMPREGNATING THE MOLDED PARTICLE BOARD WITH MOISTURE FOR A PERIOD OF TIME OF AT LEAT SEVERAL HOURS UNTIL AN AMOUNT OF WATER OF AT LEAST ABOUT 20 UP TO 100% BY WEIGHT OF SAID BOARD IS PICKED UP BY SAID BOARD TO THEREBY SWELL THE THICKNESS FROM ABOUT 7% TO ABOUT 30%, THEN DRYING THE MOISTURE TREATED BOARD UNTIL THE MOISTURE CONTENT IS REDUCED BELOW 20% AND DOWN TO 6% BY WEIGHT OF SAID DRY SHEET AND TRIMMING THE DRIED SHEET TO REDUCE THE THICKNESS TO THE PRE-DETERMINED VALUE WHEREBY A DIMENSIONALLY STABILIZED BOARD IS PRODUCED. 